fishing offshore in a rowboat.

I wouldn't be rowing through Oregon surf, but if forced too, I'd be looking at a very generous bouyancy band of lightweight flexible foam right around the gunwales, won't be in the water in normal situation, so won't interfere with rowing. Even these little tubs seem to benefit:
http://www.boatcollar.com.au/videos1.html

 

Thanks for posting those flowmo. I was having trouble looking them up before. Gorgeous.

 

Yes but it's the voids/fewer number of plys compared to $$ Joubert okume/ general behavior of fir when peeled resulting in a miserable surface to finish that makes it a second choice compared to the good stuff - particularly in a lightweight build. A few voids in thin ply can be a critical fault when you are talking 3 ply 1/4.

Depends entirely on the interplay between supporting structures & the skin. You seem to be leaning towards watertight compartments which should be thought of as the framing/bulkheads/seating etc. It that case the boat starts to look semi-monocoque in construction. So the skin thickness depends on the design of the internal structure and vice versa. It's certainly ballpark...
On a similar tack you mention styrofoam filled compartments - with strip/stitch & glue/glued lap using epoxy based liquid joinery it's simple to make airtight compartments, in fact you have to think about heated air expansion the joints are so good...so I don't see the need for styrofoam. Relatively cheap deck plates give you storage/inspection options.

Mr Efficiency has a good idea - in fact the Monomoy surf boats had a row of cork rings around the gunnel if my memory serves me right...

Confused by your use of the term "rocker". It usually refers to the degree of longitudinal curvature in the keel or bottom - you seem to be applying it to the "upturn" at the ends - different beast I think.

Hurts my brain to assemble your written build ideas into visualizable working drawings...but go for it! Personally I think mostly with a pencil - at least that's how I find out the weaknesses...

All this talk about fir 1/2" (12.7)mm bottoms, 3/8" (9.5mm) ply inner hull and screwing & gluing has got the YIKES! WEIGHT! warning light flashing on my design dashboard. If you really want foam in there consider a structural sandwich approach. Make the foam contribute structurally. Be a god awful goo fest though...

If you dropped the beach launch requirement I wouldn't broken record the weight issue (weight issue, weight issue, weight issue...) but your current construction approach ignores a ton of available info on homebuilt lightweight boatbuilding techniques - perhaps you have home building experience? That was my main obstacle to understanding the strength of 3/16" (5mm) (or less) okume when held in column by structural fillets. Moe

 

Moe, even though the described structure would be air tight to begin with, seams can fail. Home building experience, not much but grew up arround handy people. Dad was always changing or adding to the house. So yes, that is an influence. Foam would eliminate air density change issues. With wood I would be concerned that internal pressure could cause splitting if air heats up. Or I suppose hatches could be opened as needed. I went to yaquina head national park yesturday. It looks like there is a lot of good water accessable to the newport jetty. The design challenge would get a lot easier if beaching were more a matter of last resort crash landing than normal launching procedure. There is a beach access on the north beach that would be easy to get a car through but ov course it is pedestrians only. I plan to check out depot bay soon but ran out of light yesturday. I am beginning to think universal beach launch means a very small boat.

 

rocker

I think you are right. I am a little unclear on the distinction. Perhaps a pacific power dory has upturn on the bottom forward since the bottom is straight along most of the baseline. But a mckenzie river dory has a heavily rockered bottom. If the bottom of the boat is straight aft but turns up on bottom along half the length forward, would this count as rocker or upturn? Iv thought of the smileyness of the gunnel in profile as "sheer" in the past but now I wonder if there is a better word. Also I've considered the angle of a v as deadrise.

 

Love the boatcollar. I think something like that may get included in the final design.

 

simplifying the headache

I can't seem to get my machine to upload my sketches. That is why I am doing these verbally.

A minimum surf skiff trial balloon. (Crew is likely to drown)

Construction sheet plywould on taped chines instant boat style.

Two 15.75 ft by 2 ft sides

Cut matching 45 degree diagonals on the ends to rake the stems.
The resulting side panals should look like trapzoids.

Mount onto a frame 30 wide at chine 42 at sheer locate frame 1 foot forward of midships.

Bring the ends to stems and glue on a bottom.

Put a seat in the middle and an innertube at each end under 4 foot long decks.

Good luck.

 

The typical Atlantic coast beach launched dory has about 2 to 2 1/2 in. of rocker. (Newfoundland version)This seems to be the accepted amount after some hundreds of years of evolution. The McKenzie and Pacific dories are modifications of the Atlantic Dory to suit their specific requirements. The McKenzie has extreme rocker to allow it to literally spin on a dime, change direction and avoid ledges and rocks in the fast running rivers. This is not what you want in a beach launch as it would be more susceptible to broaching especially with only one set of oars in the water. I understand thinking: using rocker to acquire maneuverability and running up on a sea but keep in mind there are tradeoffs, with broaching being the big negative. My present dory (exercise machine,) is another modification of the traditional beach launch dory. It evolved over many years driven by the need of fisherman to beach launch into surf loaded with 4 to 5 lobster traps and one rower. When launching into the surf the traps occupy more or less aft to midship with the rowing station more forward. Once the traps are dumped (set) the rowing station is changed to about midship for general fishing and beaching (surfing in). About 18ft. LOA and known as the Shelbune it has about 1 to 2 in. of rocker plus a beautiful long schooner bow for surf. This also compliments directional handling due to less lateral resistance in the forefoot (underwater bow section) It's schooner bow design enhances lift upon an approaching wave "heading out into it" and beaching (surfing in) it is just progressively buoyant enough to reduce digging in (tripping)when a following sea lifts the stern. Another interesting feature is the normally flat sided traditional dory design has been rounded to run down and blend into a much narrower than traditional flat bottom. My impression on the whole package is 75% dory, 25% pea pod. I have made only one small change, I have added a long tapered skeg from midship to stern to improve directional (course keeping) sightless rowing. On long travel legs i maneuver to locate a buoy or two spaced landmarks and use ranging to keep on course. I have at times sleep rowed ala sleep walked and pre skeg verses post skeg has vastly improved my navigation -- Overall I can't see how one could improve upon the design much. I think it would be a case of slight mods to adapt for a particular need or to enhance some concern over open water safety. Presently I have very positive floatation from glassed in closed cell foam compartments, bow, stern, and under the seats. Decking over was an option but loss of interior movement space was too great a trade off. All in all I am very happy with it's rowing performance. I have no problem maintaining 3.5 to 4.5 knots over a 10 mile row. At between 275 and 300 lbs. displacement I do at times find her a little light in rough and windy conditions. I have toyed with the idea of installing two water ballast tanks, say around a cubic foot each for just these conditions. Anyhow thought i'd throw this out there as further input to your project ---Geo.

 

Or a tightly engineered & cleverly built larger one...It's a tough design problem and if you could drop that design requirement you would have a boat much easier to design & build. Also a bigger heavier boat would still be a kick to beach launch with a few friends so you don't close out that option completely. Your "competition" in the solo beach launch fishing goal is the kayak - and it's tough to improve on it...it would be an interesting challenge for me that's for sure.

Your general building plan (as I understand it) is sound & straight forward & there's just an awful lot of ways to build a good boat - but not so many if the thing has to be light enough to safely carry two people from walk to beaches.

Be nice to see some sketches - when you click "Manage Attachments"http://www.boatdesign.net/forums/newattachment.php?t=49076&poststarttime=1388513210&posthash=7a72e3b1d1d3cc86f58bcbd6ddbc069b
it gives you many options to post image file types if they aren't too big.

Thanks for that first hand account Viking North Geo. Your descriptions of the interactions between rocker, bow shape & buoyancy are first rate. Interesting that you'd like more weight in the hull once the wind blows - shows the trade-offs between launching convenience & seakeeping ability. I googled "Shelbune" but came up with squat - any links or photos to your hull type would be greatly appreciated.Moe

 

I am off to the shop now to work on my build but will post photos of the dory when i get a break. I don't think any actual lines for this boat presently exist as the plug used to make the mold was an actual old Shelburne dory that was faired up prior too. It is now being used as a big flower box entrance to the Shelburne yacht club. With modern powered fishing boats and facilities this style has gone the way of the Great Auk. A docter in Shelburne (Nova Scotia) had the mold taken off with the idea of producing and selling these great craft and presently has the mold and a few unfinished hulls. The cost factor verses the economy has pretty well put those plans in limbo. If after checking with him he has not taken the lines off and he has no objection it was always in my plans to take her lines off if for nothing else than to preserve the design for future builders. If you decide this is the boat for you I could speed up the process and do it this spring but part of my plan was to forward my numbers to a designer to have them properly reproduced. Once that is done they could be available for a very basic fee to recover my time and costs, which of course might not be necessary if upon checking her lines already exists. Meanwhile I will post some photos to give you a better idea of what she looks like, maybe from those you will have enough info to work with on your own design. If you need any basic measurements I would be happy to pass those along.--Geo.

 

Is this Gartside boat similar?



More info on the Gartside Shelburne skiff here

 

Shelburne Dory

A few photos from bare hull to finish, note that long sweeping schooner bow in the top left photo, the very narrow almost double ended stern in the top middle photo and that pea pod look in the middle bottom photo.

 

Bregaland --yes i think along similar lines but some notable differences. I think the Gartside has less rocker, less freeboard less sheer,and less sweep aft in the bow. Also since there is no cross section i can't tell about the rounded sides . Hard to tell from a limited drawing verses the actual boat.

 

Geo, your boat looks a lot like what gardiner, the author of the dory book and building classic small craft, calls generally a swampscott dory with some range on the dimensions. He claims in the dory book that the swampscott type predates straight-sided dorys and shares a common ancestor with the wherry and sea-bright skiff. What about your boat is distinct from the swampscott dory. From the photos it looks to fit the general definition.

I am not suprised that a little weight is helpful. I built my 12ft dory skiff in 1/4 inch ply with oak stem and mahogany transom. It hardly seams to touch the water. Waves on the lake don't bother it a bit but the hull is all the sail you need downwind.

 

Well if so, so be it, . I just know here it is known as the Shelburne. Maybe a boatbuilder from Shelbourne introduce the craft into other regions. Definately it's been around here for over 100yrs. Regardless it is a good surf and rowing dory. I know i've built and rowed my share. Happy New Year to you and the best of luck on your build ---Geo.